The present invention relates generally to tools used in subterranean wells and, in a preferred embodiment thereof, more particularly provides a linear indexing apparatus and methods of using same.
Due to their very nature, subterranean wells are typically axially elongated, their axial lengths being orders of magnitude greater than their diameters. For this reason, tools utilized in subterranean wells frequently employ axial displacement in their operations. As an example, many packers are set by axially displacing an inner mandrel relative to an outer case.
Where such tools are remotely positioned in subterranean wells, only a limited number of actions may be taken at the earth's surface to control operation of the tools. A tubing string from which a tool is suspended may be manipulated at the earth's surface by, for example, rotating or axially displacing the tubing string. Pressure may be applied, for example, to the interior or exterior of the tubing string. Fluid may be flowed at predetermined rates through the tubing string. These methods are well known in the art and have been utilized to operate tools in subterranean wells for many years.
In some circumstances, however, it would be beneficial for a well operator to have additional methods at his disposal for controlling tools. For example, the well operator may desire to control a particular tool by applying pressure to the interior of the tubing string, but, due to the fact that spurious pressure spikes may be encountered, other pressure-operated tools are present in the tubing string, etc., the well operator may also desire to operate the particular tool only when a predetermined number of pressure applications have been accomplished. In this manner, the well operator can avoid inadvertently operating the particular tool, essentially giving the well operator an additional degree of freedom in controlling the particular tool's operation.
A number of mechanisms have been designed which require a predetermined number of cycles to cause a certain function to occur in a tool. However, these mechanisms are not capable of incrementally indexing a component of a tool, are expensive to manufacture, are sensitive to debris, and/or a combination of the above. What is needed is an apparatus which enables a well operator to incrementally and linearly index a component of a tool, such that the tool may be operated by multiple incremental indexes of the component.
From the foregoing, it can be seen that it would be quite desirable to provide a linear indexing apparatus which is relatively inexpensive to manufacture, is capable of incrementally indexing a component of a tool in a subterranean well, and is relatively insensitive to debris. It is accordingly an object of the present invention to provide such a linear indexing apparatus and associated methods of using same.